Investigation into apparent WA virus spike

An apparent surge in a painful mosquito-borne virus in Western Australia could be put down to false positive laboratory results.

In the year to the end of July, WA's health department had been notified of 864 cases of Barmah Forest virus.

It is only found in Australia and causes symptoms including aching and swollen joints, sore muscles and tendons, skin rashes, fever, tiredness, headaches and swollen lymph nodes.

The figure was up 19 from a fortnight earlier, and a huge jump compared to the 99 cases in 2012 and 98 in 2011.

A department spokeswoman said there had been a higher than expected number of reports of the illness, from both metropolitan and regional areas of the state, since late 2012.

"Laboratory test results are only part of the information used by doctors to diagnose Barmah Forest virus infections and need to be considered with the history and symptoms of the illness in the patient," she said.

"When considered in this way, it appears that many of the recent positive laboratory reports for Barmah Forest virus do not indicate true infection.

"The WA Department of Health is currently investigating the reason for the high number of false positive laboratory results."

At the same time, there's concern about another mosquito-borne virus, Chikungunya, which is on the rise in Asia and has made its way to Australia.

In the year to July 29, 32 cases of the illness were reported in WA, compared to one in 2012 and four in 2011.